In this study, a two-step control methodology is developed for energy-optimal reconfiguration of satellites in formation in the presence of uncertainties or external disturbances. First, based on a linear deterministic system model, an optimal control law is analytically determined such that a satellite maneuvers from an initial state to a final state relative to another satellite. The structure of

Ground‐based technological systems, such as power grids, can be affected by geomagnetically induced currents (GIC) during geomagnetic storms and magnetospheric substorms. This motivates the necessity to numerically simulate and, ultimately, forecast GIC. The prerequisite for the GIC modeling in the region of interest is the simulation of the ground geoelectric field (GEF) in the same region. The modeling

The average daily natural background dose was computed with a statistical approach from the dose records of personal dosemeters worn by professionally exposed workers in Switzerland. The values ranged between 1.3–3.0 μSv/day depending on the geographic location of the customers site. The highest values were found in the Lepontine Alps, the lowest in the Swiss Plateau. The results from measurements

Microquasars (MQs) are binary systems composed by a star feeding mass to a compact object through an accretion disk. The compact object, usually a black hole, launches oppositely directed jets which are typically observed in our galaxy through their broadband electromagnetic emission. These jets are considered potential galactic neutrino sources. MQs can also have been formed by the first generations

This paper introduces a new approach of estimating the daytime horizontal geomagnetic field (∆H) induced variations of vertical E × B drift velocity and evaluates its performance using Communication/Navigation Outage Forecasting Systems (C/NOFS) over the East African sector. H‐field at AAE (Addis Ababa magnetometer station) and ETHI (Adigrat magnetometer station in Ethiopia) and their immediate difference

Landau gauge longitudinal and transverse gluon propagators are studied in lattice QCD with gauge group SU(2) at varying temperature and quark density. In particular, it is found that the longitudinal propagator decreases with increasing quark chemical potential at all temperatures under study, whereas the transverse propagator increases with increasing quark chemical potential at T<200 MeV and does

As we collectively welcome the new year, we retrace the 2020 milestones in sample return and look at a few of the major upcoming events in 2021. There are many reasons for astronomers to be optimistic.

HORuS, a new high-resolution spectrograph for the Gran Telescopio Canarias, will facilitate an expanded range of optical and near-infrared studies, explains Instrument Scientist Carlos Allende Prieto.

High-resolution observations have revealed that rotating structures known as “chromospheric swirls” are ubiquitous in the solar chromosphere. These structures have circular or spiral shapes, are present across a broad range of spatial and temporal scales and are considered as viable candidates for providing an alternative mechanism for the heating of the chromosphere and corona. Therefore, an accurate

Since realising the idea that a man-made object can be intentionally placed into the Earth’s orbit, almost 10,000 satellites have been launched for multiple scientific, commercial and military purposes. These activities produce a huge amount of junk comprised not only of defunct artificial objects that no longer serve a useful purpose, but various collisions, explosions and leaks have produced millions

An Erratum to this paper has been published: https://doi.org/10.1134/S1990341320040057

Abstract—We present the results of observations of radial velocity variability in stars with exoplanets. Observations of a number of stars with characteristic stellar magnitudes from 8.54m to 10.5m were carried out using a new high-resolution (R = 35 000–120 000) fiber-fed spectrograph mounted at the foundation of the 6-m BTA telescope, in the mode of resolutions from R = 45 000 to R = 65 000 with

Abstract—We present the measurements of masses of two exoplanets and one exoplanet candidate: the candidate we earlier confirmed in the KOI-974 system, a new TESS candidate in the TOI-1797 system, and the well-known hot Jupiter MASCARA-3b. The observations were carried out using the first prototype of the high-resolution fiber-opticspectrograph of the 6-m BTA telescope, and with the BOES spectrograph

Abstract—In this work a search was carried out for globular clusters belonging to the Sagittarius (Sgr) tidal stream using the analysis of spatial positions, radial velocities relative to the Galactic Standard of Rest (VGSR), proper motions and ratio of “age–metallicity” ([Fe/H]) for globular clusters and for stars in the tidal stream. As a result, three categories of globular clusters were obtained:

Abstract—We briefly discuss the stages of the development of high-resolution spectroscopy methods used with the 6-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences, which are related to the problem considered. We consider the possibility of the multiple increase of the stellar spectroscopy efficiency as a result of application of state-of-the-art solutions in the

Abstract—The features of the simplest inner structures of a magnetic field, the central dipole and the shifted dipole, are considered. Their secular stability, solidity of rotation, and a great variety of orientations of magnetic dipoles and magnitudes of magnetic fields are noted.

Abstract—The paper describes Zeiss-1000, the one meter telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences (SAO RAS), the history of the development of its observation methods and potential areas of astrophysical research. Detailed attention is paid to instruments and methods of observation which are in service nowadays.

Abstract—We investigate statistical patterns in the distribution of the orbits of long-period comets that belong to the inner region of the Oort cloud (with aphelion distances, Q, lying in the 50–2000 AU interval). We show that the distribution of aphelia is not random and such patterns can be due, in particular, to the presence of hypothetical massive bodies in the region considered. We varied the

Abstract—Several parameters of the Pleiades cluster were estimated. We used Gaia DR2 data on the coordinates, proper motions, and radial velocities of stars in regions with radius d° =2.5° and size 60° × 60° around the cluster center. Based on data on stars with magnitudes mG ≤ 18m, we constructed a map and profile of the density, luminosity and mass functions of the cluster, determined the cluster

Abstract—Based on the SDSS catalog data the properties of galaxies with quenched star formation (QGs) within the “splashback”-radius of galaxy clusters Rsp and beyond it have been studied. We used a sample of 40 groups and galaxy clusters and a sample of field galaxies at 0.02 < z < 0.045. The radii Rsp were defined from the observed integral distribution of the number of galaxies as a function of

Abstract—According to the exact positions and proper motions of the three components of the star ADS48 from Gaia DR2, their parallax and radial velocities for the epoch 2015.5 the instantaneous relative positions and motions of the components were determined. Only from the Gaia DR2 observations, the family of orbits of the AB pair was calculated by the method of apparent motion parameters, from which

Abstract—The nearby dwarf galaxy NGC 3077 is known for its peculiar morphology, which includes numerous dust lanes and emission-line regions. The interstellar medium in this galaxy is subject to several perturbing factors. These are primarily the central starburst and tidal structures in the M81 group. We present a comprehensive study of the state of ionization, kinematics, and chemical composition

Abstract—Based on the archival images from the Hubble Space Telescope, we performed the photometry of the brightest galaxies of the Dorado group: NGC 1433, NGC 1533, NGC 1566, and NGC 1672. In the obtained CM-diagrams, red giants are specified, and distances to galaxies are measured by the TRGB method. The estimates obtained: 14.2 ± 1.2, 15.1 ± 0.9, 14.9 ± 1.0, and 15.9 ± 0.9 Mpc show that all the

Abstract—The paper provides a review of important results of studies of chemically peculiar and related magnetic stars. More than 90 papers published in the world leading astronomical journals mainly in 2019 were analyzed. The most important results: high-accuracy photometric light curves were obtained during the TESS satellite; we discovered several dozen of new chemically peculiar magnetic stars;

Stellar models often use relations between the temperature T and optical depth τ to evaluate the structure of their optically thin outer layers. We fit a novel analytic function to the Hopf function q ( τ ) of a radiation-coupled hydrodynamics simulation of near-surface convection with solar parameters by Trampedach et al. The fit is accurate to within 0.82% for the solar simulation and to within 13%

A research project on the activities of solar-type stars based on the LAMOST sky survey was initiated recently. We describe the data processing workflow of the project and perspective on scientific yields.

An extensive analysis of the Mn spectrum was carried out using high-resolution Fourier transform (FT) and grating spectroscopy of Mn–Ne and Mn–Ar hollow cathode discharge sources, over the range 82–5500 nm (1820–121,728 cm −1 ). Spectral wavelengths for a total of 6019 Mn ii lines have been measured, of which 1345 are obtained through FT spectroscopy. These wavelengths are given to at least an order

We present the Solar Bayesian Analysis Toolkit (SoBAT), which is a new easy to use tool for Bayesian analysis of observational data, including parameter inference and model comparison. SoBAT is aimed (but not limited) to be used for the analysis of solar observational data. We describe a new IDL code designed to facilitate the comparison of a user-supplied model with data. Bayesian inference allows

We present powderday (available at https://github.com/dnarayanan/powderday [https://github.com/dnarayanan/powderday] ), a flexible, fast, open-source dust radiative transfer package designed to interface with both idealized and cosmological galaxy formation simulations. powderday builds on fsps stellar population synthesis models, and hyperion dust radiative transfer, and employs yt to interface between

We present a major update to the 3D coronal rope ejection (3DCORE) technique for modeling coronal mass ejection flux ropes in conjunction with an approximate Bayesian computation (ABC) algorithm that is used for fitting the model to in situ magnetic field measurements. The model assumes an empirically motivated torus-like flux rope structure that expands self-similarly within the heliosphere, is influenced

We present an analytical solution of a highly magnetized jet/wind flow. The left side of the general force-free jet/wind equation (the “pulsar” equation) is separated into a rotating and a nonrotating term. The two equations with either term can be solved analytically, and the two solutions match each other very well. Therefore, we obtain a general approximate solution of a magnetically dominated jet/wind

We present the first results from the Fundamental Reference active galactic nucleus (AGN) Monitoring Experiment, an observational campaign dedicated to understanding the physical processes that affect the apparent positions and morphologies of AGNs. In this work, we obtained simultaneous Swift X-ray Telescope and Very Long Baseline Array (VLBA) radio observations for a snapshot campaign of 25 local

We study a sample of 16 Type Ia supernovae (SNe Ia) having both spectroscopic and photometric observations within 2–3 days after the first light. The early B − V colors of such a sample tend to show a continuous distribution. For objects with normal ejecta velocity (NV), theC ii λ 6580 feature is always visible in the early spectra, while it is absent or very weak in the high-velocity (HV) counterpart

We measure the environmental dependence, where environment is defined by the distance to the third nearest neighbor, of multiple galaxy properties inside the Environmental COntext (ECO) catalog. We focus primarily on void galaxies, which we define as the 10% of galaxies having the lowest local density. We compare the properties of void and non-void galaxies: baryonic mass, color, fractional stellar

We investigate the dispersion measure (DM) and scattering of fast radio bursts (FRBs) by the intergalactic medium (IGM), foreground halos, and host halos using cosmological hydrodynamical simulation. We find that the median DM caused by foreground halos is around 30% of that caused by the IGM, but it has a much larger variance. The DM induced by hosts deviates from a log-normal distribution but exhibits

This work extends the computational model EULAG-MHD to include Hall magnetohydrodynamics (HMHD)—important to explore physical systems undergoing fast magnetic reconnection at the order of the ion inertial length scale. Examples include solar transients along with reconnections in magnetosphere, magnetotail, and laboratory plasmas. The paper documents the results of two distinct sets of implicit large-eddy

We present results from the “Mint” resolution DC Justice League suite of Milky Way–like zoom-in cosmological simulations, which extend our study of nearby galaxies down into the ultrafaint dwarf (UFD) regime for the first time. The mass resolution of these simulations is the highest ever published for cosmological Milky Way zoom-in simulations run to z = 0, with initial star (dark matter) particle

We explore stellar population properties separately in the bulge and the disk of double-component cluster galaxies, to shed light on the formation of lenticular galaxies in dense environments. We study eight low-redshift clusters from the Sydney-AAO Multi-object Integral field Galaxy Survey, using two-dimensional photometric bulge–disk decomposition in the g , r , and i bands to characterize galaxies

Tidal disruption events (TDEs) offer a unique opportunity to study a single supermassive black hole (SMBH) under feeding conditions that change over timescales of days to months. However, the primary mechanism for generating luminosity during the flares remains debated. Despite the increasing number of observed TDEs, it is unclear whether most of the energy in the initial flare comes from accretion

We analyze the spectra of 10 Green Pea galaxies, previously studied by Henry et al., using a semi-analytical line transfer model to interpret emission and absorption features observed in UV galactic spectra. We focus our analysis on various ionization states of silicon, associated with the cool (∼10 4 K) and warm (∼10 5 K) gas. By analyzing low-ionization lines, we study the relationships between the

We present the results of a pilot Hubble Space Telescope (HST) imaging study of the host galaxies of ten quasars from the Sloan Digital Sky Survey Reverberation Mapping (SDSS-RM) project. Probing more than an order of magnitude in black hole (BH) and stellar masses, our sample is the first statistical sample to study the BH–host correlations beyond z > 0.3 with reliable BH masses from reverberation

We present a systematic numerical relativity study of the dynamical ejecta, winds, and nucleosynthesis in neutron star (NS) merger remnants. Binaries with the chirp mass compatible with GW170817, different mass ratios, and five microphysical equations of state (EOSs) are simulated with an approximate neutrino transport and a subgrid model for magnetohydrodynamic turbulence up to 100 ms postmerger.

Recent data suggest that the Universe could be positively curved. Combined with an inflationary stage, this might lead to a curvature bounce instead of the Big Bang. The background evolution is presented, as a function of the parameters controlling the cosmic evolution. The primordial tensor spectrum is also calculated and possible observational footprints of the model are underlined. Several potentials

The Fisher gAlaxy suRvey cOde (FARO) is a new public Python code that computes the Fisher matrix for galaxy surveys observables. The observables considered are the linear multitracer 3D galaxy power spectrum, the linear convergence power spectrum for weak lensing, and the linear multitracer power spectrum for the correlation between galaxy distribution and convergence. The code allows for tomographic

Charged, rotating Kerr-Newman black holes represent the most general class of asymptotically flat black hole solutions to the Einstein-Maxwell equations of general relativity. Here, we consider a simplified model for the Hawking radiation produced by a Kerr-Newman black hole by utilizing a (1+1)-dimensional accelerated boundary correspondence (i.e. a flat spacetime mirror trajectory) in Minkowski spacetime

The observation of primordial correlators by cosmological surveys is a very promising avenue to probe high energies and the perturbative regime of quantum gravity. Hence, it is imperative that we understand how these observables are shaped by the pillars of fundamental physics, namely unitarity, locality and symmetries. To this end, we study the three-point correlators of gravitons and scalar curvature

Loop corrections to the power spectrum are frequently computed using approximate non-linear kernels adopted from an Einstein de-Sitter (EdS) cosmology. We present an algorithm that allows us to take the full time- and scale-dependence of the underlying fluid dynamics into account, and apply it to assess the impact of neutrino free-streaming on the 1- and 2-loop matter power spectrum. Neutrino perturbations

Using a multi-field stochastic approach, we investigate the vacuum expectation value (VEV) during inflation of a scalar field charged under a mildly broken global U(1) symmetry that can play the role of baryon or lepton number, or possibly a dark baryon number or a combination of the three. Even for a CP invariant Lagrangian, the stochastic distribution of inflationary VEVs in general breaks CP spontaneously

Baryon asymmetry via non-thermal leptogenesis is explained in the framework of the standard Coleman-Weinberg inflationary model. The CP-violation asymmetry factor arises from the out-of-equilibrium decays of heavy right-handed neutrinos in supersymmetric SO(10) GUT models. All quantities of interest are computed in terms of the two parameters of the inflationary potential, namely the vacuum expectation

Magnetars are the most highly magnetized neutron stars in the cosmos (with magnetic field 1013–1015 G). Giant flares from magnetars are rare, short-duration (about 0.1 s) bursts of hard X-rays and soft γ rays1,2. Owing to the limited sensitivity and energy coverage of previous telescopes, no magnetar giant flare has been detected at gigaelectronvolt (GeV) energies. Here, we report the discovery of

Nearby galaxies offer unique laboratories allowing multi-wavelength spatially resolved studies of the interstellar medium, star formation and nuclear activity across a broad range of physical conditions. In particular, detailed studies of individual local luminous infrared galaxies (LIRGs) are crucial for gaining a better understanding of these processes and for developing and testing models that are

The three-body recombination of oxygen atoms O + O + M → O2(el) + M is the dominant process of oxygen excitation in the Earth’s nightglow at altitudes of 85–110 km. The rate coefficient of this reaction, as well as the quantum yields of electronically excited products (O2(el) in the electronic states: 5πg, A3Σu+, A′3Δu, c1Σu+, b1Σg+, a1Δg, X3Σg-) depend on the gas kinetic temperature. In addition to

Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS) is a tracking technique based on a one-way ground to space Doppler link. For Low Earth Orbit (LEO) satellites, DORIS shows a robust capability in terms of data coverage and availability, due to a wide and well-distributed ground network, where data are made available by the International Doris Service (IDS). However, systematic

The eastern part of the Rich area consists of the massive Paleozoic and Meso-Cenozoic cover formations that present the geodynamic development of the study area, where is characterized by various carbonate facies of Jurassic age. The geographical characteristic of the study area leaves the zone difficult to map by conventional methods. The objective of this work focuses on the mapping of the constituent

Shorelines constantly vary due to natural, urbanization and anthropogenic effects such as global warming, population growth, and environmental pollution. Sustainable monitoring of coastal changes is vital in terms of coastal resource management, environmental preservation and planning. Publicly available Landsat 8 OLI (Operational Land Manager) images provide accurate, reliable, temporal and up-to-date

This paper presents an improved new method with differential evolution and the cubic spline approach is proposed to retrieve sea level height based on GNSS SNR observations from a single geodetic receiver. Considering the B-spline function is unstable at the beginning or end, and the feature that B-spline functions do not pass through nodes may introduce errors. Thus, the cubic spline is applied to

Lake water height is a key variable in water cycle and climate change studies, which is achievable using satellite altimetry constellation. A method based on data processing of altimetry from several satellites has been developed to interpolate mean lake surface (MLS) over a set of 22 big lakes distributed on the Earth. It has been applied on nadir radar altimeters in Low Resolution Mode (LRM: Jason-3

Mean night-time peak power, Doppler shift and Doppler width of spread Doppler clutter (SDC) received by a high frequency backscatter radar located at Alice Springs, Australia from 2000 to 2018 is presented as a function of azimuth, sunspot number, time of year and frequency. The sampled region covers 90 degrees from West to North and includes the northern and southern equatorial anomalies. SDC peak

Within a quantum hydrodynamic model and using the reductive perturbation technique, the nonlinear ion-acoustic wave (IAW) excitations due to a moving charged object in an electron-pair-ion quantum plasma are studied both analytically and numerically. In such quantum plasmas we have derived forced Korteweg-de Vries (fKdV) type equation for finite amplitude nonlinear IAWs. The effect of relevant plasma

As an important error source in Global Navigation Satellite System (GNSS) positioning and ionospheric modeling, the differential code biases (DCB) need to be estimated accurately, e.g., the regional Quasi-Zenith satellite system (QZSS). In this paper, the DCB of QZSS is estimated by adopting the global ionospheric modeling method based on QZSS/GPS combined observations from Multi-GNSS experiment (MGEX)